BY MEANS OF A VIBRATING VOLTAGE PROBE (NVPPD) THE GERMAN COCKROACH, BLATTELLA GERMANICA, AND AMERICAN COCKROACH, PERIPLANETA AMERICANA, OVARIAN FOLLICLES WERE SHOWN SEVERAL YEARS AGO TO PASS LARGE IONIC CURRENTS CORRELATED WITH THE PRESUMPTIVE LOCATION ON THE EMBRYONIC GERM BAND (ANIMAL POLE). BY USING ION SUBSTITUTION IT WAS LATER CONCLUDED THAT THE OBSERVED OUTWARD CURRENT AT THE VEGETAL POLE CONSISTED OF AN OUTWARD K+ CURRENT WHILE AN OBSERVED INWARD (+) CURRENT AT THE VEGETAL POLE WAS CAUSED BY AN OUTWARD CL- CURRENT. THIS LATER CONCLUSION HOWEVER HAS RECENTLY BEEN SHOWN TO BE IN ERROR BY WORK HERE AT THE NVP FACILITY, USING SELECTIVE ION ELECTRODES. THIS DISCOVERY ALSO THROWS DOUBT ON OTHER CONCLUSIONS REACHED VIA ION SUBSTITUTION. IN A SABBATICAL YEAR AT THE NVP FACILITY J. KUNKEL USED A K+ VIBRATING SPECIFIC ION ELECTRODE (NVPK) TO DEMONSTRATE A SUBSTANTIAL K+ CURRENT EMANATING FROM THE FOLLICLE CELL LAYER AT THE PRESUMPTIVE DORSAL POLE (VEGETAL) AND AN INWARD K+ CURRENT AT THE VENTRAL POLE (ANIMAL). THE PRIOR EVIDENCE FROM THE NVPPD USING ION SUBSTITUTION IS THUS SUSPECT WHEN USING THE MORE DIRECT MEASUREMENT OF SPECIFIC ION MOVEMENTS. A 2-D VERSION OF THE NVPK SOFTWARE WAS USED TO MAP THE PATTERN OF K+ CURRENT IN B. GERMANICA AND P. AMERICANA OOCYTES. A 3-D VERSION OF THE PROBE SOFTWARE HAS ALLOWED FURTHER DEMARCATION OF THE EXTENT OF THE ACTIVE EPITHELIUM.